The invention relates to a beverage preparation device, in particular a coffee machine, even more preferably having a heating and/or foaming device for milk, having a disk valve, comprising a valve housing and a disk stack arranged therein, having a, preferably ceramic, cover disk that has at least one fluid opening, preferably configured as a fluid inlet opening, for fluid, in particular water and/or steam, and having at least one control disk that is arranged on a side of the cover disk facing away from an outer end side of the cover disk, wherein the control disk is rotatable, manually and/or by means of a drive, about an axis of rotation relative to the cover disk between different selection positions (in order to set different fluid flows). Thus, by means of the control disk, rotation-angle-dependent selection positions of the disk valve configured as a selector valve are settable, wherein, depending on the rotation angle setting, ducts or passages of the valve are open or closed.
The invention also relates to an operating method.
In beverage preparation devices, in particular coffee machines with a milk heating and/or foaming function, ceramic disk valves comprising a disk stack are used, which can, as selector valves, connect a selected drain line of a hot-water and/or steam generator to a selected feed line of a functional element, for example a nozzle, in a rotation-angle-dependent manner. The known ceramic disk valves in beverage preparation devices generally consist of two ceramic disks, arranged in a stationary manner, with passage openings and a control disk arranged in a sandwiched manner between the outer rotationally fixed ceramic disks, said control disk being assigned an electromotive drive in order for it to be possible to rotate the control disk relative to the stationary disks and thus for it to be possible to perform relative rotation-angle settings, wherein different fluid paths are open and/or closed in the different rotation angle settings.
EP 1 300 105 B1 describes that the ceramic disks are force-loaded toward one another by means of a spring, in order to ensure sufficient tightness.
EP 1 916 459 B1 likewise describes a beverage preparation device having a disk valve. In the known control valve, the cross-sectional area of the feed and drain lines corresponds to the cross-sectional areas of the fluid openings, assigned thereto, in the stationary ceramic disks.
DE 44 27 745 A1 discloses a multidisk distribution valve for coffee or espresso machines, in which, axially next to a cover disk, a sealing element having through-openings is arranged, which are aligned with fluid openings in the cover disk. In this case, the cross-sectional area of the through-openings in the sealing element is slightly larger than the cross-sectional area of the assigned fluid opening in the cover disk. Formed on the sealing element in the region of the through-openings are sealing lips which are intended to ensure efficient contact pressure of the sealing disk against the cover disk.
As further prior art, DE 10 2008 041 122 A1 and DE 27 53 264 A1 are mentioned.
In the known ceramic disks, the contact pressure and thus the sealing force is constant in all operating situations and can decrease over the lifetime of the beverage preparation device on account of dwindling spring forces of pressure springs that are used, and this can result in tightness problems between the individual disks or of the ducts formed therein.